Typescript type inference for 'decode' function in nip19 is not working fully

nip17.test.ts

@@ -4,7 +4,7 @@ import { decode } from './nip19.ts'
 import { wrapEvent, wrapManyEvents, unwrapEvent } from './nip17.ts'
 import { hexToBytes } from '@noble/hashes/utils'
 
-const senderPrivateKey = decode(`nsec1p0ht6p3wepe47sjrgesyn4m50m6avk2waqudu9rl324cg2c4ufesyp6rdg`).data as Uint8Array
+const senderPrivateKey = decode(`nsec1p0ht6p3wepe47sjrgesyn4m50m6avk2waqudu9rl324cg2c4ufesyp6rdg`).data
 
 const sk1 = hexToBytes('f09ac9b695d0a4c6daa418fe95b977eea20f54d9545592bc36a4f9e14f3eb840')
 const sk2 = hexToBytes('5393a825e5892d8e18d4a5ea61ced105e8bb2a106f42876be3a40522e0b13747')

nip19.test.ts

@@ -1,17 +1,14 @@
-import { test, expect, describe } from 'bun:test'
-import { generateSecretKey, getPublicKey } from './pure.ts'
+import { describe, expect, test } from 'bun:test'
 import {
   decode,
   naddrEncode,
-  nprofileEncode,
-  npubEncode,
-  nsecEncode,
   neventEncode,
-  type AddressPointer,
-  type ProfilePointer,
-  EventPointer,
   NostrTypeGuard,
+  nprofileEncode,
+  npubEncode,
+  nsecEncode
 } from './nip19.ts'
+import { generateSecretKey, getPublicKey } from './pure.ts'
 
 test('encode and decode nsec', () => {
   let sk = generateSecretKey()
@@ -38,7 +35,7 @@ test('encode and decode nprofile', () => {
   expect(nprofile).toMatch(/nprofile1\w+/)
   let { type, data } = decode(nprofile)
   expect(type).toEqual('nprofile')
-  const pointer = data as ProfilePointer
+  const pointer = data
   expect(pointer.pubkey).toEqual(pk)
   expect(pointer.relays).toContain(relays[0])
   expect(pointer.relays).toContain(relays[1])
@@ -67,7 +64,7 @@ test('encode and decode naddr', () => {
   expect(naddr).toMatch(/naddr1\w+/)
   let { type, data } = decode(naddr)
   expect(type).toEqual('naddr')
-  const pointer = data as AddressPointer
+  const pointer = data
   expect(pointer.pubkey).toEqual(pk)
   expect(pointer.relays).toContain(relays[0])
   expect(pointer.relays).toContain(relays[1])
@@ -86,7 +83,7 @@ test('encode and decode nevent', () => {
   expect(nevent).toMatch(/nevent1\w+/)
   let { type, data } = decode(nevent)
   expect(type).toEqual('nevent')
-  const pointer = data as EventPointer
+  const pointer = data
   expect(pointer.id).toEqual(pk)
   expect(pointer.relays).toContain(relays[0])
   expect(pointer.kind).toEqual(30023)
@@ -103,7 +100,7 @@ test('encode and decode nevent with kind 0', () => {
   expect(nevent).toMatch(/nevent1\w+/)
   let { type, data } = decode(nevent)
   expect(type).toEqual('nevent')
-  const pointer = data as EventPointer
+  const pointer = data
   expect(pointer.id).toEqual(pk)
   expect(pointer.relays).toContain(relays[0])
   expect(pointer.kind).toEqual(0)
@@ -121,7 +118,7 @@ test('encode and decode naddr with empty "d"', () => {
   expect(naddr).toMatch(/naddr\w+/)
   let { type, data } = decode(naddr)
   expect(type).toEqual('naddr')
-  const pointer = data as AddressPointer
+  const pointer = data
   expect(pointer.identifier).toEqual('')
   expect(pointer.relays).toContain(relays[0])
   expect(pointer.kind).toEqual(3)
@@ -133,7 +130,7 @@ test('decode naddr from habla.news', () => {
     'naddr1qq98yetxv4ex2mnrv4esygrl54h466tz4v0re4pyuavvxqptsejl0vxcmnhfl60z3rth2xkpjspsgqqqw4rsf34vl5',
   )
   expect(type).toEqual('naddr')
-  const pointer = data as AddressPointer
+  const pointer = data
   expect(pointer.pubkey).toEqual('7fa56f5d6962ab1e3cd424e758c3002b8665f7b0d8dcee9fe9e288d7751ac194')
   expect(pointer.kind).toEqual(30023)
   expect(pointer.identifier).toEqual('references')
@@ -145,7 +142,7 @@ test('decode naddr from go-nostr with different TLV ordering', () => {
   )
 
   expect(type).toEqual('naddr')
-  const pointer = data as AddressPointer
+  const pointer = data
   expect(pointer.pubkey).toEqual('3bf0c63fcb93463407af97a5e5ee64fa883d107ef9e558472c4eb9aaaefa459d')
   expect(pointer.relays).toContain('wss://relay.nostr.example.mydomain.example.com')
   expect(pointer.relays).toContain('wss://nostr.banana.com')

nip19.ts

@@ -70,31 +70,46 @@ export function decodeNostrURI(nip19code: string): ReturnType<typeof decode> | {
   }
 }
 
-export function decode(code: string):
-  | {
-      type: 'nevent'
-      data: EventPointer
-    }
-  | {
-      type: 'nprofile'
-      data: ProfilePointer
-    }
-  | {
-      type: 'naddr'
-      data: AddressPointer
-    }
-  | {
-      type: 'npub'
-      data: string
-    }
-  | {
-      type: 'nsec'
-      data: Uint8Array
-    }
-  | {
-      type: 'note'
-      data: string
-    } {
+export type DecodedNevent = {
+  type: 'nevent'
+  data: EventPointer
+}
+
+export type DecodedNprofile = {
+  type: 'nprofile'
+  data: ProfilePointer
+}
+
+export type DecodedNaddr = {
+  type: 'naddr'
+  data: AddressPointer
+}
+
+export type DecodedNsec = {
+  type: 'nsec'
+  data: Uint8Array
+}
+
+export type DecodedNpub = {
+  type: 'npub'
+  data: string
+}
+
+export type DecodedNote = {
+  type: 'note'
+  data: string
+}
+
+export type DecodedResult = DecodedNevent | DecodedNprofile | DecodedNaddr | DecodedNpub | DecodedNsec | DecodedNote
+
+export function decode(nip19: NEvent): DecodedNevent
+export function decode(nip19: NProfile): DecodedNprofile
+export function decode(nip19: NAddr): DecodedNaddr
+export function decode(nip19: NSec): DecodedNsec
+export function decode(nip19: NPub): DecodedNpub
+export function decode(nip19: Note): DecodedNote
+export function decode(code: string): DecodedResult
+export function decode(code: string): DecodedResult {
   let { prefix, words } = bech32.decode(code, Bech32MaxSize)
   let data = new Uint8Array(bech32.fromWords(words))
 

nip29.ts

@@ -2,7 +2,7 @@ import { AbstractSimplePool } from './abstract-pool.ts'
 import { Subscription } from './abstract-relay.ts'
 import type { Event, EventTemplate } from './core.ts'
 import { fetchRelayInformation, RelayInformation } from './nip11.ts'
-import { AddressPointer, decode } from './nip19.ts'
+import { AddressPointer, decode, NostrTypeGuard } from './nip19.ts'
 import { normalizeURL } from './utils.ts'
 
 /**
@@ -518,11 +518,11 @@ export async function loadGroupFromCode(pool: AbstractSimplePool, code: string):
  * @returns A GroupReference object if the code is valid, otherwise null.
  */
 export function parseGroupCode(code: string): null | GroupReference {
-  if (code.startsWith('naddr1')) {
+  if (NostrTypeGuard.isNAddr(code)) {
     try {
       let { data } = decode(code)
 
-      let { relays, identifier } = data as AddressPointer
+      let { relays, identifier } = data
       if (!relays || relays.length === 0) return null
 
       let host = relays![0]